The present invention relates broadly to thermoplastic reinforced hoses for low, medium, or high pressure applications, and more particularly to a construction therefor which results in a hose having improved flexibility.
Thermoplastic reinforced hose is used in a variety of fluid transfer applications. In basic structure, hoses of the type herein involved may be conventionally constructed as having a tubular core surrounded by one or more reinforcement courses of natural or synthetic fiber and/or steel wire. The reinforcement courses, in turn, are protected by a surrounding outer sheath or cover which may be of the same or different material as the core tube. The cover also provides the hose with increased abrasion resistance.
The core tube, which may be a thermoplastic material such as a polyamide, polyolefin, polyvinyl chloride, fluoropolymer, or polyurethane, or a synthetic rubber material such as Buna-N or neoprene, is conventionally extruded and cooled or cured. As is detailed in U.S. Pat. Nos. 3,116,760; 3,159,183; 3,966,238; 4,952,262, if necessary, the tube may be cross-head extruded over a mandrel for support, or otherwise supported in later forming operations using air pressure and/or reduced processing temperatures.
From the extruder, the tube may be collected on a reel or other take-up device for further processing. As dispensed from the reel, the tube optionally next may be passed through an applicator for its coating with an outer layer of an adhesive material which, in the case of thermoplastic hose, may be a polyurethane or other isocyanate-based adhesive. The core tube then may be delivered through a braider and/or a spiral winder for its reinforcement with one or more surrounding layers of a wire and/or fibrous material or blend such as a monofilament, yarn, cord, yarn-wire composite, or roving. As is described in Japanese (Kokai) Publ. No. 10-169854 A2, Canadian Patent No. 973,074, and U.S. Pat. Nos. 3,654,967; 3,682,201; 3,790,419; 3,861,973; 3,905,398; 4,007,070; 4,064,913; 4,343,333; and 4,898,212, these reinforcement layers, which are applied under tension and which may be bonded to the core and to adjacent reinforcement layers, typically comprise an interwoven braid or a spiral winding of a nylon, polyester, polyphenylene bezobisoxazole, polyvinyl acetate, or aramid yarn, or a high tensile steel or other metal wire.
Following the application of the reinforcement layers, the outer cover or sheath optionally may be applied. Such cover, which may be formed as a cross-head extrusion, a moisture-cured or solvent-based dipped coating, or a spiral-wound wrapping, typically comprises an abrasion-resistant polymeric material such as a polyamide, polyolefin, fluoropolymer, polyvinyl chloride, or polyurethane. As before, an adhesive layer may be used to bond the outer cover to the reinforcement layers. Representative hose constructions, as well as manufacturing methods and materials therefor, are shown in U.S. Pat. Nos. 1,281,557; 3,566,924; 3,654,967; 3,682,202; 3,707,178; 3,773,089; 3,779,308; 3,790,419; 3,791,415; 3,805,848; 3,881,975; 3,889,716; 3,890,181; 3,905,398; 3,914,146; 3,932,559; 3,966,238; 3,982,982; 3,988,188; 4,000,759; 4,098,298; 4,111,237; 4,142,554; 4,175,992; 4,182,019; 4,148,963; 4,241,763; 4,259,991; 4,273,160; 4,294,636; 4,364,266; 4,317,000; 4,342,612; 4,343,333; 4,380,252; 4,384,595; 4,444,707; 4,456,034; 4,459,168; 4,463,779; 4,522,235; 4,537,222; 4,553,568; 4,585,035; 4,652,475; 4,668,318; 4,699,178; 4,850,395; 4,898,212; 4,952,262; 5,024,252; 5,062,456; 5,361,806; 5,609,962; 5,698,278; 5,778,940; and 5,862,623.
In normal use, such as in mobile or industrial hydraulic applications, hoses of the type herein involved may be exposed to a variety of environmental factors and mechanical stresses which cannot always be predicted. Of utmost importance to the integrity and performance of the hose is that a strong bond is achieved between the constituent parts thereof. However, while it is important to bond these parts together, it is also important that the hose not be made overly stiff so as to make it prone to kinking or fatigue or otherwise useable for certain applications.
In view of the foregoing, it will be appreciated that hose constructions must exhibit a demanding balance of chemical and physical properties. Indeed, as commercial applications for hoses continue to increase, it is believed that improvements in hose constructions would be well-received by numerous industries. Especially desired would be a construction which is flexible and light-weight, yet resistant to external stresses in a variety of mobile and industrial applications.
The present invention is directed to thermoplastic reinforced hoses, and particularly to a construction therefor which results in a hose which is resistant to environmental conditions and mechanical stresses, but which is still flexible. Accordingly, the hose construction of the invention is adapted for use in a variety of applications such as for mobile or industrial hydraulic installations specifying working pressures of between about 150-12,000 psi (1.0-82.7 MPa).
Advantageously, the hose of the present invention includes a bonding agent such as an adhesive layer which may be interposed between each successive pair of reinforcement layers to effect a strong chemical or other bond therebetween. Importantly, however, the viscosity and other physical or chemical properties of the bonding agent and/or the reinforcement are controlled so as not to saturate the reinforcement layers which would increase the stiffness and weight of the resulting hose.
In an illustrated embodiment, the hose construction of the present invention includes a core tube over which at least a pair of fibrous reinforcement layers are braided or wound to provide resistance to internal pressure. A protective cover is provided over the reinforcement layers. The innermost reinforcement layer may be bonded to the core, and the outermost reinforcement layer may be bonded to the cover, using conventional solvating techniques. Each reinforcement layer is bonded to the next outermost layer with an adhesive layer interposed therebetween. The adhesive layer, which may be a solvent-based adhesive or a resin such as a thermoplastic hot-melt, is applied so as not to saturate the reinforcement layers.
The present invention, accordingly, comprises the article and method of its manufacture possessing the construction, combination of elements, and arrangement of parts and steps which are exemplified in the detailed disclosure to follow. Advantages of the present invention include a hose construction which is light-weight, abrasion-resistant, and flexible, but which also is highly resistant to internal and external conditions and stresses. Additional advantages include a collapse-resistant, high pressure hose construction which is manufacturable in relatively long lengths and is adaptable for use in a variety of fluid transfer applications, and which, if desired, may be made electrically non-conductive or static dissipative. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.